Integrated circuits (ICs) are the basic building blocks that are used to create electronic devices. Continuous improvements in IC process and design technologies have led to smaller, more complex, and more reliable electronic devices at a lower cost per function. As performance has increased and size and cost have decreased, the use of ICs has expanded significantly.
One particular type of IC that would benefit from inexpensive mass production involves the use of radio frequency identification (RFID) technology. RFID technology incorporates the use of electromagnetic or electrostatic radio frequency (RF) coupling. Traditional forms of identification such as barcodes, cards, badges, tags, and labels have been widely used to identify items such as access passes, parcels, luggage, tickets, and currencies. However, these forms of identification may not protect items from theft, misplacement, or counterfeit, nor do they allow “touch-free” tracking.
More secure identification forms such as RFID technology offer a feasible and valuable alternative to traditional identification and tracking. RFID does not require physical contact and is not dependent on line-of-sight for identification. RFID technology is widely used today at lower frequencies, such as 13.56 MHz, in security access and animal identification applications. Higher-frequency RFID systems ranging between 850 MHz and 2.5 GHz have recently gained acceptance and are being used in applications such as vehicular tracking and toll collecting, and in business logistics such as manufacturing and distribution.
A printing process is used to print conductive traces on a substrate to form a functional electronic structure such as an RFID antenna. The RFID antenna absorbs, couples with, and/or reflects radio frequency signals from a transmitter and provides a signal and power to an attached integrated circuit. The conductance of the antenna is determined by material properties of the antenna and the thickness of the conductive traces. For example, some areas of the antenna may need to conduct more current than other areas of the antenna; therefore, a greater amount of conductive material must be used when higher current density is required. However, a process such as screen printing applies a single layer of film of conductive ink at a generally constant thickness.